Rob
I have a similar set up to you and had quite a few problems getting it right.
One tip - you need to make sure you don't overload the mount. I have a SN 8" and an ED80 - too heavy to guide with sadly. I compromised and picked up a Stellarvue 60M finder. With a 2x barlow and a DSI it is light enough to use with the bigger scope.
Second tip - download the pulse guide driver for ASCOM from Craig Star's site.
Third tip - have a read about my efforts here -
http://www.iceinspace.com.au/forum/s...light=phd+pete
You might find a solution in there somewhere
Furth tip - join the Yahoo users group for PHD. You'll probably find a solution among the FAQ. If not, post your query and you'll get a quick and helpful response. That was my experience.
Hope that helps - oh, and have a crack at drift alignment. You need to be close to guide sensibly. The best tutorial I found was on Cloudy Nights.
Good luck
Pete